Factorio SA 2.0.55
After some other mods updated, my savegame threw this error. Had to completely remove, re-save and re-load. Now it works but I thought I report anyway.

The mod Kuxynator's Production Rates (3.2.12) caused a non-recoverable error.
Please report this error to the mod author.

Error while running event Kux-ProductionRates::on_configuration_changed
__Kux-ProductionRates__/modules/ViewStorage.lua:47: attempt to index local 'viewStorage' (a nil value)
stack traceback:
    __Kux-ProductionRates__/modules/ViewStorage.lua:47: in function <__Kux-ProductionRates__/modules/ViewStorage.lua:39>
    (...tail calls...)
    __Kux-ProductionRates__/gui/ProductionRatesFrame.lua:349: in function 'refresh_gui'
    __Kux-ProductionRates__/gui/ProductionRatesFrame.lua:769: in function 'fnc'
    __Kux-CoreLib__/lib/EventDistributor.lua:136: in function <__Kux-CoreLib__/lib/EventDistributor.lua:131>

thanks for reporting
I've implemented something now, but without a reproducible case I can't truly test it.

I couldn't reproduce it on a new game, only while loading my savegame, I think it was caused by one of the other mod's updates. The error message is gone now. Probably planet Rubia mod, if I have to take a guess.